Curated Optogenetic Publication Database

Abstract: Optogenetics is the genetic approach for controlling cellular processes with light. It provides spatiotemporal, quantitative and reversible control over biological signaling and metabolic processes, overcoming limitations of chemically inducible systems. However, optogenetics lags in plant research because ambient light required for growth leads to undesired system activation. We solved this issue by developing plant usable light-switch elements (PULSE), an optogenetic tool for reversibly controlling gene expression in plants under ambient light. PULSE combines a blue-light-regulated repressor with a red-light-inducible switch. Gene expression is only activated under red light and remains inactive under white light or in darkness. Supported by a quantitative mathematical model, we characterized PULSE in protoplasts and achieved high induction rates, and we combined it with CRISPR-Cas9-based technologies to target synthetic signaling and developmental pathways. We applied PULSE to control immune responses in plant leaves and generated Arabidopsis transgenic plants. PULSE opens broad experimental avenues in plant research and biotechnology.

Abstract: The immune system distinguishes between self and foreign antigens. The kinetic proofreading (KPR) model proposes that T cells discriminate self from foreign ligands by the different ligand binding half-lives to the T cell receptor (TCR). It is challenging to test KPR as the available experimental systems fall short of only altering the binding half-lives and keeping other parameters of the interaction unchanged. We engineered an optogenetic system using the plant photoreceptor phytochrome B (PhyB) as a ligand to selectively control the dynamics of ligand binding to the TCR by light. This opto-ligand-TCR system was combined with the unique property of PhyB to continuously cycle between the binding and non-binding states under red light, with the light intensity determining the cycling rate and thus the binding duration. Mathematical modeling of our experimental datasets showed that indeed the ligand-TCR interaction half-life is the decisive factor for activating downstream TCR signaling, substantiating KPR.

Abstract: Optogenetic tools to control gene expression have many advantages over the classical chemically inducible systems, overcoming intrinsic limitations of chemical inducers such as solubility, diffusion, and cell toxicity. They offer an unmatched spatiotemporal resolution and permit quantitative and noninvasive control of the gene expression. Here we describe a protocol of a synthetic light-inducible system for the targeted control of gene expression in plants based on the plant photoreceptor phytochrome B and one of its interacting factors (PIF6). The synthetic toggle switch system is in the ON state when plant protoplasts are illuminated with red light (660 nm) and can be returned to the OFF state by subsequent illumination with far-red light (760 nm). In this protocol, the implementation of a red light-inducible expression system in plants using Light-Emitting Diode (LED) illumination boxes is described, including the isolation and transient transformation of plant protoplasts from Arabidopsis thaliana and Nicotiana tabacum.